Method and system for latching an actuator

ABSTRACT

An axle disconnect system including an actuator having an energizable coil in an overmold that is at least partially surrounded by a coil housing. An armature is in sliding engagement with the housing such that the magnetic flux through the magnetic circuit is uninterrupted. Disposed between one of (i) the housing or armature and (ii) a sliding collar is a slide ring. The sliding collar is located directly radially inward from the slide ring. A first end portion of the sliding collar has a set of axially extending teeth. Radially inward from the first end portion of the sliding collar is a return spring groove having a return spring. An outer surface of a second end portion of an output gear has a set of axially extending teeth that are selectively engageable with the teeth on the first end portion of the sliding collar.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 62/023,944 filed on Jul. 13, 2014, which is herein incorporated by reference in its entirety to the extent permitted by law.

FIELD OF THE INVENTION

The present invention relates to methods and systems for latching an actuator where the actuator has no, or minimal, magnetic gap. In certain embodiments, the invention relates to actuators for use in power take-off units or vehicular drivetrain systems, such as differentials, axle disconnect systems, or power transfer units. In a specific embodiment, the invention relates to an actuator for use in an axle disconnect system.

BACKGROUND OF THE INVENTION

In the automotive industry, actuators are used for a number of purposes, including in drivetrain systems such as differentials, axle disconnect systems, or power transfer units. As just one example, typical all-wheel drive systems for vehicles push torque through a torque coupling to the secondary axle to provide enhancements in performance, handling and mobility. These systems require that the secondary axle, and the rest of the driveline, be continually rotating at road speed, which reduces the overall efficiency of the vehicle, and reduces fuel economy.

Secondary axle disconnects are available and they permit the secondary axle and prop shaft to stop rotating. These disconnect systems increase vehicle efficiency, but the current systems also require power to both engage and disengage the output and/or remain engaged or disengaged. The latter situation may require constant power to the system, which reduces overall system efficiency, or may require the use of permanent magnets.

As is known in the art, the actuator converts electrical current into mechanical force. The flow of electrical current into the actuator creates a magnetic field that moves a metal armature which, via additional mechanical elements, results in a change in the engagement/disengagement status of the particular drivetrain system, such as the axle disconnect system described briefly above.

Traditionally, when the actuator was energized, the armature would be drawn towards the solenoid as a result of the magnetic field generated, engaging the axle disconnect system. If it was desirable to keep the system engaged, either current would have to be continually applied or permanent magnets would have to be included in the design of the actuator so that the armature would stay in the engaged position. For obvious reasons, it is not desirable to have a solenoid draw significant power when holding the system engaged (or disengaged).

Latching solenoids can also accomplish maintained engagement with a permanent magnet in the system. Use of permanent magnets has undesirable consequences such as temperature demagnetization and shock demagnetization. In addition, depending on the material, permanent magnets can be costly, difficult to fasten, and can be fragile.

It would be desirable for a system to maintain vehicle efficiency by using an actuator that did not require continuous power or permanent magnets to stay engaged.

The current invention utilizes certain design features, certain low cost magnetic steels, and a connect/disconnect strategy that will control current to the actuator. It does not use any separate permanent magnet component(s), thus achieving the same desired result with no design sacrifices or additional cost.

SUMMARY OF THE INVENTION

The invention described herein includes an actuator in an engaged state that is made up of the following: a unenergized coil of copper windings disposed in an overmold, a housing at least partially surrounding the coil, an armature in sliding engagement with the housing, and wherein magnetic flux is uninterrupted between the armature and at least one of the coil or housing.

The invention herein also describes an axle disconnect system that when engaged, includes the following: an actuator with an unenergized coil of copper windings disposed in an overmold, a housing at least partially surrounding the coil, and an armature in sliding engagement with the housing, wherein magnetic flux is uninterrupted between the armature and at least one of the coil or housing. The axle disconnect system may also include a rotatable and axially slidable slide ring located between at least one of (i) the coil housing or armature and (ii) a sliding collar, the slide ring with a radially outer surface, a radially inner surface, a first end and a second end. The sliding collar has a first portion and a second portion. The first portion is located directly radially inward from the slide ring and defines a first portion defining a first set of axially extending teeth. The second portion located radially inward from the first portion; a return spring groove located radially inward from the sliding collar first portion and housing a return spring therein; and an output gear with a second set of axially extending teeth for engagement with the sliding collar first set of teeth.

Also described herein are methods of maintaining engagement of an axle disconnect system. The methods include providing an axle disconnect system with an actuator. The actuator has an electromagnetic coil comprising copper windings in an overmold, a housing at least partially surrounding the coil, and an armature in sliding engagement with the housing. The methods also include the step of energizing the electromagnetic coil, thereby causing a magnetic flux in at least one of the electromagnetic coil, coil housing, or armature, which causes the armature to move from a first axial position to a second axial position where the magnetic flux is uninterrupted between the electromagentic coil housing and armature. Once the armature is in the second axial position, the method includes de-energizing the electromagnetic coil. Maintaining the armature in the second axial position where the magnetic flux is uninterrupted between the electromagnetic coil housing and armature is also included in the methods.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description when considered in the light of the accompanying drawings in which:

FIG. 1 is a partial cut-away perspective view a typical axle disconnect system using an embodiment of an actuator in accordance with the invention. The actuator is in the unengaged position.

FIG. 2 shows a schematic cross sectional view of a second embodiment of an actuator in accordance with the invention. The actuator is shown in the unengaged state.

FIG. 3 shows a schematic cross sectional view of an engaged actuator as known in the prior art.

FIG. 4 shows a schematic cross sectional view of an engaged actuator in accordance with embodiments of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific assemblies, articles and features illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts. Hence, specific dimensions, directions, or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting, unless expressly stated otherwise. Also, although they may not be, like elements in various embodiments may be commonly referred to with like reference numerals within this section of the application.

For use in this description only, the terms actuator and solenoid can be used interchangeably.

Turning now to FIG. 1, one example of an axle disconnect system 10 for use with the embodiments of the invention is shown. The system 10 comprises an electromagnet 12 including a coil 14 and a coil housing 16. The coil housing 16 is hollow and encloses the coil 14. The coil 14 comprises multiple copper wire windings encased in a potting material 18 within the coil housing 16. The wire windings of the coil 14 are connected to a source for electricity (not shown).

The coil housing 16 may be one piece or several pieces that have been connected together.

A slide ring 20 is located between the coil housing 16 and a sliding collar 22. More particularly, the slide ring 20 is located radially inward from the coil housing 16 and is in direct contact therewith. The slide ring 20 is constructed of a metallic material that is susceptible to magnetic forces, such as steel.

The slide ring 20 can have a complementary shape to the coil housing 16.

An arm 24 extends radially inward from the slide ring 20. A first side 26 of the inwardly extending arm 24 is located axially adjacent a first bushing 28. A second side 30 of the inwardly extending arm 24 is adjacent the sliding collar 22. The slide ring 20 is adapted for selective axial movement.

The first bushing 28 is located between the slide ring 20 and the sliding collar 22. The first bushing 28 is a continuous, ring-shaped structure. The first bushing 28 is constructed of a non-magnetic material, such as, but not limited to, plastic.

The sliding collar 22 is located directly radially inward from the slide ring 20 and directly radially outward from an output shaft (not shown), and has a first portion 34 and a second portion 36. The first and second portions 34, 36 are unitary and one-piece with one another. More particularly, the first portion 34 is located directly radially inward from the slide ring 20 and extends radially outward parallel to the radially inwardly extending arm 24 of the slide ring 20. The first portion 34 of the sliding collar 22 has a first set of axially extending teeth 38.

The second portion 36 is located radially inward from the first portion 34, and extends in an outward direction parallel with the output shaft (not shown). The second portion 36 defines a first set of axially extending splines 40. The splines 40 are integrally formed and unitary with the sliding collar 20 and allow for axial movement along the output shaft 32.

A return spring groove 42 as also depicted in FIG. 1, is located radially inward from the first portion 34 of the sliding collar 22. The return spring groove 42 receives a return spring 44 therein. A first end 46 of the return spring 44 abuts an end of the return spring groove 42. A second end 48 of the return spring 44 abuts a snap ring 50.

An output gear 52 is located radially inward from the slide ring 20 and radially outward from the output shaft (not shown). An outer surface 54 of the output gear 52 defines a second set of axially extending teeth 56 for engaging the first set of axially extending teeth 38 on the sliding collar 22. The engagement of the teeth sets 38, 56 rotationally locks the sliding collar 22 with the output gear 52.

The system has two modes of operation. In a first mode of operation as depicted in FIG. 1, the sliding collar 22 and the output gear 52 are not connected or rotating together, but sometimes it is desired that they be connected so that they rotate together. When this mode is to be used, electricity is sent to the coil 14 and the coiled wires create a magnetic flux. In other words, the current in the coil 14 causes the coil housing 16 to become magnetized. The sum of the coil flux and the housing magnetism is greater than the sum of the spring force and friction force of the slide ring 20, which causes the slide ring 20 to move. Within a few milliseconds of the coil 14 being energized, the magnetic flux contributes to the magnetic slide ring 20 moving in the axial direction. The slide ring 20 axially moves the first bushing 28, which in turn axially moves the sliding collar 22 pushing the sliding collar 22 into engagement with the output gear 52.

As the first mode is being engaged, the first set of teeth 38 on the sliding collar 22 are not engaged with the second set of teeth 56 on the output gear 52; a gap separates the two sets of teeth 38, 56. However, as the sliding collar 22 is moved, the gap separating the two sets of teeth 38, 56 closes. In a short amount of time, on the order of milliseconds, the gap is closed and the first set of teeth 38 on the sliding collar 22 engage with the second set of teeth 56 on the output gear 52. Upon engagement of the two sets of teeth 38, 56, the sliding collar 22 is rotationally fixed to the output gear 52. The rotation from the sliding collar 22 is transferred through the output gear 52 to the output shaft (not shown).

In prior art systems, when it is desired that the components no longer be engaged, the electricity to the coil 14 is interrupted. The return spring 44 pushes against the sliding collar 22 thus urging it axially away from the output gear 52. The biasing of the return spring 44 separates the two sets of teeth 38, 56. The return spring 44 permits the system 10 to default to a position where the components are not engaged. When the sliding collar 22 is not engaged with the output gear 52, the system 10 is in the mode as depicted in FIG. 1.

The current invention, however, utilizes an actuator designed with a continuous magnetic circuit (no/minimal air gaps), such that, when energized, the surfaces mate and provide sufficient contact to allow any residual magnetism in the components to have a continuous path.

The permanent flux from the coil housing 16 is strong enough to hold the sliding collar teeth 38 in engagement with the output gear teeth 56. Therefore, if power is turned off to the coil 14, the system 10 will stay in the engaged position. Therefore, the system does not require power to stay in the engaged position. This is advantageous since it can operate in the engaged position without continuing to draw electrical power, which makes the system more efficient.

When it is desired that the system 10 no longer be engaged, a current is provided to the coil 14 to create a flux in the opposite direction. The flux would demagnetize the coil housing 16. The spring 44 pushes against the sliding collar 22 thus urging it axially away from the output gear 52. The biasing of the spring 44 separates the two sets of teeth 38, 56. When the sliding collar 22 is not engaged with the output gear 52 the system is in the second mode.

FIG. 2 shows a cross-sectional view of an unengaged actuator 100 in accordance with one embodiment of the invention. The actuator 100 includes an electromagnetic coil 110. The electromagnetic coil 110 is composed of a coil housing 120, a cover 130, an armature 140, and copper wire windings 150 encased in potting material or overmold 160. The cover 130 can have, but is not necessary, a nub 180. The nub 180 extends axially from the inner radial end 190 of the cover 130. The armature 140 has a first end 200 that, in an unengaged state, is separated from the nub 180. The armature has a second end 210 of a shape complementary to that of the housing 120 and can abut the housing 120 when in an unengaged state.

Also shown is a slide ring 170 that abuts and is complementary to the armature 140.

The cover 130, coil housing 120, and armature 140 will all be made of a ferrous metal that has residual magnetism. Such metals can be a high carbon steel, such as, but no limited to 1014 steel or 1065 steel.

Upon activation, power is supplied to the copper windings 150, which, within a few milliseconds, creates a magnetic flux in at least one of the coil housing 120, the cover 130 and the armature 140. The coil housing 120, the cover 130 (if present) and the armature create a magnetic circuit through which the magnetic flux can travel. The magnetic flux acts on the ferrous material of the armature 140, causing it to move. After activation, the first end 200 of the armature 140 comes into contact with the nub 180 of the cover 130. The second end 210 of the armature 140 has less contact with the coil housing 120. The movement of the armature 140 causes the slide ring 170 to move, thereby engaging the rest of the system.

Although this actuator 100 is shown, various embodiments are contemplated to be within the scope of the invention, including actuators with differently shaped covers, armatures and housings. The way the armature and housing interact can vary, as can how the armature and cover interact upon engagement. The actuator 100 shown is just one of many possibilities. One important aspect of the invention is that the actuator be able to stay engaged, or latch, even when continuous power is not being supplied to the coil. In order to accomplish this without the use of a permanent magnet, there must be no or minimal magnetic gap between the armature and the rest of the electromagnetic coil. FIGS. 3 and 4 are illustrative.

FIG. 3 shows engagement a very generic electromagnetic coil 300 as would be seen in the prior art. The electromagnetic coil 300 consists of copper windings 310 in a potting or overmold 320. The copper windings 310 and overmold 320 are contained in a housing 330 with a cover 340. The armature 350 can selectively move in the axial direction (indicated by the arrow). In this figure, the electromagnetic coil 300 is engaged. In typical prior art systems, a magnetic gap 360 remains between the armature 350 and the cover 340 even during activation of the coil 300.

Conversely, the actuators of the invention, as shown generically in FIG. 4 have no magnetic gap and generally the armature 350 will contact the housing 330 or cover 340 (depending on precise design of actuator) through contact point 370. Precise and complete contact through contact point 370 is not necessary. A minimal gap or partial gap may be permissible as long as the magnetic flux traveling through magnetic circuit of the coil housing 330, cover 340, and/or armature 350 is uninterrupted and strong enough to keep the electromagnetic coil 300 latched. It is important to note that, if the system in which the electromagnetic coil 300 is used has other forces working on the armature, such as, but not limited to, the pull of a return spring (as depicted in more detail in the first embodiment), the residual magnetism in the magnetic circuit of the electromagnetic coil 300 will have to be strong enough to overcome those opposing forces.

Details of the interface between the armature 350 and rest of the electromagnetic coil 300 can be manipulated to affect the holding force (e.g. parallel butt-face or chamfered interface provide different holding force).

Residual magnetism varies within the common steels available. In most cases, materials are chosen to reduce/eliminate this nuisance property. By properly selecting the grade of steel, the holding force can be defined for a given solenoid design. One non-limiting example can be high carbon steels such as, but not limited, 1014 steel or 1065 steel. Other materials used, such as a ferrous material for the armature 350, will be those known in the art.

As residual magnetic flux may decay over time, the control solution may include periodic energy pulses to reinforce coupling strength.

With respect to releasing the coupling, once powered and the closed magnet circuit is in place, a pulse of current through the coil in the reverse direction counter-acts the flux that holds the armature and solenoid together. This pulse should be of sufficient duration to generate enough flux to counteract the flux from the retained magnetism and short enough not to cause re-engagement.

In certain applications, where vibration is high or design constraints exist that cause loss of holding force over time, it may be necessary to send an energizing pulse every so often to ensure the device maintains holding.

The control system for such a residual magnetism coupling system may be further enhanced based on other information available within the overall vehicle architecture. For example, if the vehicle dynamic control system detects a change in acceleration (e.g. yaw, pitch, roll) the control system for the coupling solution may leverage this data in an algorithm which would determine when the controller would generate a reinforcement pulse to ensure the coupling is maintained during the vehicle dynamic event.

As noted previously, the axle disconnect system described above is just one example of many systems in which the current invention can be used. Variations in axle disconnect systems might include different shapes of coil housing 16, or the addition or subtraction of other elements in the system.

Also, it can be appreciated that one embodiment of the system described and depicted herein is for an axle connect/disconnect system. However, the device described herein is not limited to just axles. Instead, the device can be applied to other devices, equipment and methods known in the automotive arts including, but not limited to, power take off units, differentials, and power transfer units. Several examples of systems that can be used with actuators of the invention can be found in U.S. patent application Ser. No. 14/606,066 which discusses several axle disconnect and power take-off unit systems, all of which could be used with actuators that take advantage of residual magnetism as described herein.

In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiments. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope. 

1-15. (canceled)
 16. An axle disconnect system, comprising, an actuator comprising: an energizable coil comprising copper windings; a housing at least partially surrounding the coil; an armature in sliding engagement with the housing, wherein magnetic flux through a magnetic circuit is uninterrupted; a rotatable and axially slidable slide ring located between at least one of (i) the coil housing or armature and (ii) a sliding collar, the slide ring comprising a radially outer surface, a radially inner surface, a first end and a second end; the sliding collar comprising a first portion and a second portion, the first portion is located directly radially inward from the slide ring, the first portion defining a first set of axially extending teeth, the second portion is located radially inward from the first portion; a return spring groove located radially inward from the sliding collar first portion and housing a return spring therein; and an output gear comprising a second set of axially extending teeth, the second set of axially extending teeth are on an outer surface of a second end portion of the output gear and the second set of axially extending teeth of the output gear are selectively engageable with the sliding collar first set of teeth.
 17. The axle disconnect system of claim 16, wherein the magnetic circuit comprises at least one of the housing, the armature, and a cover.
 18. The axle disconnect system of claim 16, wherein the actuator lacks a permanent magnet.
 19. The axle disconnect system of claim 16, wherein the first end portion of the sliding collar has an inner diameter and the second end portion of the sliding collar has an inner diameter, wherein the inner diameter of the second end portion of the sliding collar is smaller than the inner diameter of the first end portion of the sliding collar.
 20. The axle disconnect system of claim 16, wherein the second end portion of the sliding collar has a first set of splines.
 21. The axle disconnect system of claim 16, wherein the slide ring has an arm extending radially inward from the radially inner surface of the slide ring.
 22. The axle disconnect system of claim 17, wherein at least one of the housing, the cover, the slide ring or armature are composed of a ferrous material able to have residual magnetism.
 23. The axle disconnect system of claim 22, wherein the ferrous material is selected from the group consisting of: a high carbon steel, a steel having a carbon content of approximately 0.5% or more, a 1095 carbon steel and a 1065 carbon steel.
 24. The axle disconnect system of claim 16, wherein the copper windings of the of the energizable coil are encased in an overmold material or a potting material.
 25. A method of maintaining engagement of an axle disconnect system, the method comprising the steps of, (i) providing an axle disconnect system comprising an actuator, wherein the actuator comprises: an electromagnetic coil comprising copper windings disposed in an overmold; a housing at least partially surrounding the coil; an armature in sliding engagement with the housing; (ii) energizing the electromagnetic coil, thereby causing a magnetic flux through a magnetic circuit, and thereby causing the armature to move from a first axial position to a second axial position where the magnetic flux through the magnetic circuit is uninterrupted; (iii) de-energizing the electromagnetic coil; (iv) using residual magnetism of the housing and/or the armature to maintain the armature in the second axial position where the magnetic flux through the magnetic circuit is uninterrupted; and (v) maintaining the armature in the second axial position where the magnetic flux through the magnetic circuit is uninterrupted.
 26. The method of maintaining engagement of the axle disconnect system of claim 25, wherein the method further comprises the step of sending a re-energizing current pulse to the coil to ensure maintained engagement.
 27. The method of maintaining engagement of the axle disconnect system of claim 25, wherein the method further comprises the step of sending a reverse current pulse to the coil to end engagement.
 28. A method of maintaining engagement of a power take-off unit, the method comprising the steps of, (i) providing a power take-off unit comprising an actuator, wherein the actuator comprises: an electromagnetic coil comprising copper windings disposed in an overmold; a housing at least partially surrounding the coil; an armature in sliding engagement with the housing, and wherein the actuator is lacking a permanent magnet; (ii) energizing the electromagnetic coil, thereby causing a magnetic flux through a magnetic circuit and thereby causing the armature to move from a first axial position to a second axial position where the magnetic flux through the magnetic circuit is uninterrupted, (iii) de-energizing the electromagnetic coil; (iv) using residual magnetism of the housing and/or the armature to maintain the armature in the second axial position where the magnetic flux through the magnetic circuit is uninterrupted; and (v) maintaining the armature in the second axial position where the magnetic flux through the magnetic circuit is uninterrupted.
 29. A shaft connect and disconnect system, comprising, a shaft connect and disconnect system comprising: an actuator comprising an energizable electromagnetic coil; wherein the energizable electromagnetic coil comprising copper windings; wherein the energizable coil in the overmold is at least partially disposed within a coil housing; a slide ring having a radially outer surface, a radially inner surface, a first end and a second end is in sliding engagement with the soil housing; wherein a magnetic flux through a magnetic circuit is uninterrupted; wherein the slide ring is disposed between the coil housing and a sliding collar; wherein at least a portion of the radially outer surface of the slide ring is in direct contact with at least a portion of the coil housing; an arm having a first side and a second side extends radially inward from the radially inward surface of the slide ring; the sliding collar having an inner surface, an outer surface, a first end portion and a second end portion; wherein the sliding collar is disposed directly radially inward from the slide ring; wherein the first end portion of the sliding collar has a set of axially extending teeth; wherein the first end portion of the sliding collar is selectively engageable with at least a portion of the first side of the arm extending radially inward from the inner surface of the slide ring; wherein the inner surface of the second end portion of the sliding collar has a first set of splines; a return spring groove having a return spring is disposed radially inward from the first end portion of the sliding collar; an output gear comprising a set of axially extending teeth on an outer surface of a second end portion of the output gear; and wherein the set of axially extending teeth on the outer surface of the output gear are selectively engageable with the set of axially extending teeth on the first end portion of the sliding collar.
 30. The axle disconnect system of claim 29, wherein the magnetic circuit comprises at least one of the coil housing, the armature, and a cover.
 31. The shaft connect and disconnect system of claim 29, wherein the shaft connect and disconnect system selectively engages a shaft in an axle disconnect system, a power take off unit, a differential assembly or a power transfer unit.
 32. The shaft connect and disconnect system of claim 29, wherein the actuator lacks a permanent magnet.
 33. The shaft connect and disconnect system of claim 30, wherein at least one of the coil housing, the cover or the slide ring are composed of a material able to have residual magnetism.
 34. The shaft connect and disconnect system of claim 29, wherein the first end portion of the sliding collar has an inner diameter and the second end portion of the sliding collar has an inner diameter, wherein the inner diameter of the second end portion of the sliding collar is smaller than the inner diameter of the first end portion of the sliding collar.
 35. The shaft connect and disconnect system of claim 29, further comprising a bushing; wherein the bushing is a continuous ring-shaped structure made of a non-magnetic material; and wherein the bushing is axially adjacent to the first side of the arm extending radially inward from the radially inner surface of the slide ring.
 36. shaft connect and disconnect system of claim 29, wherein the copper windings of the of the energizable coil are encased in an overmold material or a potting material. 